The biosynthesis of glycoproteins in mineralizing tissues is to be investigated by light microscope (LM) and electron microscope (EM) radioautography, histochemistry, and biochemical analysis after cell fractionation. To this end, 30-40 rats will receive H3-fucose, H3- mannose, H3-glucosamine, H3-galactose or S35 sulfate intravenously and sacrifices will be made between 2 and 72 hours postinjection. Some animals will receive cycloheximide prior to isotope injection, in a dose sufficient to block H3-proline uptake into protein. Incisor teeth and surrounding bone will be processed after perfusion fixation, and labeled precursors will be traced in odontoblasts, osteoblasts and ameloblasts. After establishing intracellular sites of uptake and pathways of migration, the mode of discharge and pattern of deposition of glycoproteins into each matrix will be explored. Collagen biosynthesis will be traced in osteoblasts of chick embryo calvaria by combined radioautographic and biochemical studies utilizing 3H-proline. The organelle(s) in which procollagen peptides aggregate, and molecular modifications that occur during transport and secretion will be identified. Other glycoproteins. glycosaminoglycans, and phosphoproteins will be similarly examined. In pulse labeling experiments with osteoblasts and odontoblasts, the endoplasmic reticulum, Golgi apparatus and secretory granules will be isolated in order to clearly define their roles in the synthesis of collagen and other glycoproteins, as well as determine kinetics of transport. Thus, it is hoped to elucidate the steps involved in the elaboration of matrix glycoproteins by mineralizing tissues, and to determine their roles in the development of calcified matrices.